Field of the Disclosure
Various examples of the present disclosure relate to medical devices, systems and methods used in minimally invasive spinal surgery. More particularly, various examples of this disclosure are directed to spinal stabilization and arthrodesis by implantation of devices via a pre-sacral approach.
Description of the Related Technology
The present disclosure is an extension of work assigned to TranS1 Inc., now Baxano Surgical Inc., with a principle place of business located in Raleigh, N.C. Much of the access work is described in great detail in the many commonly-assigned applications including U.S. Pat. No. 7,530,993 which describes surgical tools, tool sets and methods for percutaneously (or minimally invasively) accessing and preparing treatment sites on the sacrum of the spine. As described in the present disclosure and application, after the spine is accessed, various devices and tools can be inserted into the spine trans-sacrally in order to treat various spinal disorders and injuries. Examples of such procedures and associated devices and tools are disclosed in additional applications including, but not limited to, U.S. Provisional Patent Application No. 60/182,748, filed Feb. 16, 2000, U.S. patent application Ser. No. 09/640,222, filed on Aug. 16, 2000 now U.S. Pat. No. 6,575,979, U.S. patent application Ser. No. 09/782,583 filed on Feb. 13, 2001, now U.S. Pat. No. 6,558,390, U.S. patent application Ser. No. 09/848,556 filed on May 3, 2001, now U.S. Pat. No. 7,014,633, U.S. patent application Ser. No. 10/125,771 filed on Apr. 18, 2002, now U.S. Pat. No. 6,899,716, U.S. patent application Ser. No. 10/309,416 filed on Dec. 3, 2002, now U.S. Pat. No. 6,921,403, U.S. patent application Ser. No. 10/972,065, filed on Oct. 22, 2004, U.S. patent application Ser. No. 11/189,943 filed Jul. 26, 2005, now U.S. Pat. No. 7,608,077, U.S. patent application Ser. No. 11/501,351, filed on Aug. 9, 2006, U.S. patent application Ser. No. 12/541,785 filed Aug. 14, 2009, U.S. Provisional Application No. 61/259,977 filed on Nov. 10, 2009 and U.S. patent application Ser. No. 12/916,463 filed Oct. 29, 2010, the contents of each of which are incorporated in their entirety into this disclosure by reference herein.
Examples of a trans-sacral approach to lumbar surgery described in certain examples of the above-referenced patents and patent applications represents a pioneering and innovative approach to spinal surgery. In addition, the surgical tools and methods described in these references provide for a minimally invasive and reproducible approach for providing access to primarily, but not limited to, the L4-L5 and L5-S1 vertebral bodies. The devices and methods described above are commercially available and are made by TranS1, Inc., now Baxano Surgical Inc., and sold under the trademark AXIALIF®. Accordingly, the background of the disclosure provided herein does not repeat all of the detail provided in the earlier applications, but instead highlights how the present disclosure adds to this body of work. Moreover, as with any implants, surgical tools and methods, there remains a need to continuingly improve such implants, tools and methods.
The spine is formed of a series of bones called vertebrae. A vertebra consists of two essential parts including an anterior segment or body, and a posterior part, or vertebral or neural arch. These two parts enclose the vertebral foramen, which together form a canal for the protection of the spinal cord. The vertebral arch consists of a pair of pedicles and a pair of laminae. The body is the largest part of a vertebra, and is generally cylindrical with flattened upper and lower surfaces. The pedicles are two short, thick processes, which project backward, one on either side, from the upper part of the body, at the junction of its posterior and lateral surfaces.
FIG. 1 shows the various segments of a human spinal column as viewed from the side. Each pair of adjacent vertebral bodies and the intervertebral space contributes to the overall flexibility of the spine (known as a motion segment) and contributes to the overall ability of the spine to flex to provide support for the movement of the trunk and head. The vertebrae of the spinal cord are conventionally subdivided into several sections. Moving from the head to the tailbone, the sections are cervical 104, thoracic 108, lumbar 112, sacral 116, and coccygeal 120. The individual segments within the sections are identified by number starting at the vertebral body closest to the head. Of particular interest in this application are the vertebral bodies in the lumbar section and the sacral section. As the various vertebral bodies in the sacral section are usually (naturally) fused together in adults, it is sufficient and perhaps more descriptive to merely refer to the sacrum rather than the individual sacral components.
The individual motion segments within the spinal columns allow movement within constrained limits and provide protection for the spinal cord. The discs are important to allow the spinal column to be flexible and to bear the large forces that pass through the spinal column as a person walks, bends, lifts, or otherwise moves. Unfortunately, for a number of reasons noted below, for some people one or more discs in the spinal column will not operate as intended. The reasons for disc problems range from a congenital defect, disease, injury, or degeneration attributable to aging. Often when the discs are not operating properly, the gap between adjacent vertebral bodies is reduced and this causes additional problems including pain.
Instability of spinal joints may result from, for example, trauma (to ligamentous structures; fracture, or dislocation); degenerative disease processes (e.g., rheumatoid arthritis; degenerative spondylosis; spondylolisthesis; spinal stenosis); tumor; infection, or congenital malformation that may lead to significant pathological translation, or longitudinal displacement. Cord compression and trauma to the spinal cord can result in respiratory distress, pain, nerve dysfunction, paresis and paralysis, or even sudden death. Therefore, the need for spinal stabilization in the setting of pathological instability is paramount.
Spinal arthrodesis, or fusion, provides needed biomechanical stability and is a therapy used to treat such instability. The objective is to create a stable biomechanical environment and provide the biological requirements for osseous fusion. Adequate decompression of the neurological structures, where indicated, and recreation of normal sagittal and coronal alignment are prerequisites prior to an arthrodesis procedure. Spinal fixation has been achieved using a variety of techniques to provide stabilization and/or spinal alignment, followed by fusion, or arthrodesis by means of bone graft insertion. Over the years, various techniques and systems have been developed for correcting spinal injuries and/or degenerative spinal processes. One class of solutions is to remove the failed disc and then fuse the two adjacent vertebral bodies together with a permanent but inflexible spacing, also referred to as static stabilization. Fusing one section together ends the ability to flex in that motion segment. However, as each motion segment only contributes a small portion of the overall flexibility of the spine, it can be a reasonable trade-off to give up the flexibility of a motion segment in an effort to alleviate significant back pain.
Thus, spinal correction frequently requires stabilizing a portion of the spine to facilitate fusing portions of the spine or other correction methodologies and medical correction of this type is frequently employed for many spinal conditions, such as, for example, degenerative disc disease, scoliosis, spinal stenosis, or the like. Frequently, these corrections also require the use of implants and/or bone grafts. Stabilizing the spine allows bone growth between vertebral bodies such that a portion of the spine is fused into a solitary unit.
Among techniques and systems that have been developed for correcting and stabilizing the spine and facilitating fusion at various levels of the spine is a system for axial trans-sacral access. One example of axial trans-sacral access to the lumbo-sacral spine as shown in FIGS. 2A and 2B below, reduces the need for muscular dissection and other invasive steps associated with traditional spinal surgery while allowing for the design and deployment of new and improved instruments and therapeutic interventions, including stabilization, mobility preservation, and fixation devices/fusion systems across a progression-of-treatment in intervention. FIGS. 2A and 2B show an example of a process of “walking” a blunt tip stylet 204 up the anterior face of the sacrum 116 to the desired position on the sacrum 116 while monitored on a fluoroscope (not shown). This process moves the rectum 208 out of the way so that a straight path is established for the subsequent steps. FIG. 2C illustrates a representative axial trans-sacral channel 212 established through the sacrum 116, the L5/sacrum intervertebral space, the L5 vertebra 216, the L4/L5 intervertebral space, and into the L4 vertebra 220.
The use of a trans-sacral approach to provide spinal therapy is described in commonly assigned U.S. Pat. Nos. 6,921,403, 7,588,574 and which are incorporated by reference into this application. A brief overview of this method of accessing the spinal region to receive therapy is useful to provide context for the present disclosure. As shown in FIG. 2A, a pre-sacral approach through percutaneous anterior track towards sacral target, through which trans-sacral axial bore will be made and the access channel extended distally for subsequent advancement of multi-level axial spinal stabilization assemblies. An anterior, pre-sacral, percutaneous tract extends through the pre-sacral space anterior to the sacrum. The pre-sacral, percutaneous tract is preferably used to introduce instrumentation to access and prepare the access channel (e.g., by drilling a bore in the distal/cephalad direction through one or more lumbar vertebral bodies and intervening discs). “Percutaneous” in this context simply means through the skin and to the posterior or anterior target point, as in transcutaneous or transdermal, without implying any particular procedure from other medical arts. However, percutaneous is distinct from a surgical access, and the percutaneous opening in the skin is preferably minimized so that it is less than 4 cm across, preferably less than 2 cm, and, in certain applications, less than 1 cm across. The percutaneous pathway is generally axially aligned with the bore extending from the respective anterior or posterior target point through at least one sacral vertebral body and one or more lumbar vertebral body in the cephalad direction as visualized by radiographic or fluoroscopic equipment.
More specifically, in one example as shown in FIG. 2B, the lumbar spine is accessed via a small skin puncture adjacent to the tip of the coccyx bone. The pre-sacral space is entered, using standard percutaneous technique, and the introducer assembly with the stylet's blunt tip serving as a dilator is placed through the paracoccygeal entry site. Once the tip of the stylet is through the facial layer, the blunt tip is rotated back against the anterior face of the sacrum and “walked” to the desired position on the sacrum under fluoroscopic guidance. Once the target site has been accessed and risk of soft tissue damage mitigated, the blunt-tipped stylet is removed and a guide pin, or wire, is safely introduced through the guide pin introducer tube, and “tapped in”. In one example, a guide pin establishes the trajectory for creating an axial bore track. In one example, the guide pin establishes the trajectory for placement of subsequent bone dilators and sheath through which a twist drill is introduced creating an axial bore track, the lumen of which is extended distally. In some examples, a presacral cage may be delivered over a wire, or a presacral cage may not be delivered over a wire. In some examples, the guide pin maintains the axial alignment of access and preparation tools as well as the alignment of cannulated spinal stabilization devices and assemblies, of larger diameter than the bore track, that are sometimes subsequently introduced over a 23″ long, 0.090″ diameter guide pin and through an exchange cannula for deployment within the vertebral column, as described at least in part in commonly assigned U.S. patent application Ser. Nos. 10/972,065, 10/971,779, 10/971,781, 10/971,731, 10/972,077, 10/971,765, 10/971,775, 10/972,299, and 10/971,780, all of which were filed on Oct. 22, 2004, and in commonly assigned United States Provisional Patent Application “Method and Apparatus for Access and Deployment of Spinal Stabilization Devices Through Tissue”, 60/706,704 filed Aug. 9, 2005, and Exchange System For Axial Spinal Procedures Ser. No. 11/501,351 filed Aug. 9, 2006, and all of which are incorporated by reference herein in their entirety.
U.S. patent application Ser. No. 12/916,463, which is hereby incorporated by reference in its entirety, discloses additional methods, techniques and devices for providing a trans-sacral approach to provide spinal therapy. For example, the tissue retraction device (not shown) can be inflated or otherwise expanded to device a working space or channel that is generally positioned between the bowl and the sacrum. The working space or channel created by the tissue retraction device can form a portal that extends from a target site on a patient's sacrum towards or to an surgical access site such that tools and instruments can be inserted from the surgical access site, through the portal and to the target site. In these examples, the tissue retraction device can serve to protect the patient's soft tissue (e.g., the bowel) as the instruments are advanced towards the target site on the sacrum. In certain examples, the tissue retraction device can provide substantially 360 degrees (about the longitudinal axis of the device) of protection about the portal. In this manner, as tools are advanced towards the access site the tissue retraction device completely surrounds such tools preventing the tools from contacting or traumatizing the soft tissues of the patient. In other examples, the tissue retraction device can form an atraumatic barrier between the tools and the bowel as tools are passed over or partially through the device. In certain examples, the tissue retraction device can also retract the bowel from the sacrum and/or dissect tissue. An advantage of certain examples is that the tissue retractor can conform to the face of the sacrum.
While stabilization procedures, and in particular surgical implants, instrumentation, and techniques, continue to evolve in the pursuit of improvements in clinical outcomes (e.g., the highest fusion rate with the shortest time to fusion and improvement in neurological function), and in simplicity of use, notwithstanding, there remains a need for ongoing advancements in spinal implant constructs and systems leading to progress in the surgical management of complex spinal disorders, to accommodate an increased spectrum of anatomical variations, to enable simplicity of instrumentation placement, and to avoid certain adverse events such as loss of spinal alignment, in order to achieve more rigid stabilization in a wider variety of spinal diseases.
There are disclosed herein various examples of surgical implants, instruments and methods for minimally invasive spinal stabilization or fusion. It is believed that the use of the systems disclosed herein will overcome limitations noted above and will result in improved maintenance of alignment, increased rate of successful arthrodesis, and minimized occurrence of adverse events as evidenced by clinical and radiographic outcomes.
General Comments and Terminology
In the context of the present disclosure, as used herein the terms “assembly” or “constructs” are sometimes used interchangeably and refer to implants, implant systems, instruments, or instruments systems which are configured to comprise multiple components, which may or may not be contiguous. It is further understood that individual components may themselves be configured as sub-assemblies, e.g., comprising a plurality of component materials, and that the formation of the components may involve intermediate processes or appliances. It is further understood that the terms spinal implants, implants, devices, cages, mini-cages, pre-sacral mini-cages and/or spacers are sometimes used interchangeably, and moreover, that “pre-sacral” refers to the fact that the devices are advanced through the pre-sacral space to subsequently access (e.g., by means of trans-sacral insertion) and be deployed into or at an intended target site for therapy, e.g., in a motion segment vertebral body or disc space.
It will also be understood that upon formation of assemblies from multiple components and deployment, individual components of the present disclosure may or may not remain as discernibly distinct. It will also be understood that, for convenience, system components may be packaged and provided either individually, or as in “kits,” and either as reusable or disposable.
As used herein, the term “biocompatible” refers to an absence of chronic inflammation response or cytotoxicity when or if physiological tissues are in contact with, or exposed to (e.g., wear debris) the materials and devices of the present disclosure. In addition to biocompatibility, in another example of the present disclosure it is preferred that the materials comprising the implant and instrument systems are sterilizable.
In one example of the present disclosure, certain components of the device assemblies and systems of the present disclosure are configured to comprise biocompatible materials and are able to withstand, without wear, multiple cycles/procedures without failing. For example, materials selected may include but are not limited to, biomedical titanium, PEEK, tantalum, machined allograft bone, cobalt-chromium, or medical grade stainless steel alloys.
It will be further understood that the length and dimensions of implant components and instruments described herein will depend in part on the target site selection of the treatment procedure and the physical characteristics of the patient, as well as the construction materials and intended functionality, as will be apparent to those of skill in the art.
In order to make it easier for a reader to find certain sections of this document that are of particular interest to the reader, a series of headings have been used. These headings are solely for the purpose of helping readers navigate the document and do not serve to limit the relevance of any particular section exclusively to the topic listed in the heading.
In the context of this discussion: anterior refers to “in front” of the spinal column; (ventral) and posterior refers to “behind” the column (dorsal); cephalad means towards the patient's head; caudal refers to the direction or location that is closer to the feet. Proximal is closer to the surgeon; distal is in use more distant from the surgeon. “Superior” refers to a top or front surface, while “inferior” refers to a back or bottom surface of a device. When referencing tools, distal would be the end intended for insertion into the patient and proximal refers to the other end, generally the end closer to, e.g., a handle for the tool and the user.
The sequence of operations (or steps) is not limited to the order presented in the claims or figures unless specifically indicated otherwise.